Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$14.26	5.675%	$15.0693	$15.07	$15.05	$15.10
Purchase #2	$153.79	12.576%	$173.1306	$173.13	$173.15	$173.10
Purchase #3	$50.66	5.811%	$53.6039	$53.60	$53.60	$53.60
Purchase #4	$33.87	10.468%	$37.4155	$37.42	$37.40	$37.40
Purchase #5	$108.51	7.119%	$116.2348	$116.23	$116.25	$116.20
Purchase #6	$81.89	10.161%	$90.2108	$90.21	$90.20	$90.20
Purchase #7	$168.27	4.467%	$175.7866	$175.79	$175.80	$175.80
7 purchase totals =	$611.25		$661.4515	$661.45	$661.45	$661.40